Triptycene derivatives, and their use for optoelectronic applications, in particular as electroluminescent materials
There is a considerable industrial demand for large-area solid-state light sources for a number of applications, predominantly in the area of display elements, display screen technology and illumination technology. The requirements made of these light sources can currently not be met entirely satisfactorily by any of the existing technologies.
As an alternative to conventional display elements, such as incandescent lamps, gas-discharge lamps and non-self-illuminating liquid-crystal display elements, electroluminescent (EL) materials and devices, such as light-emitting diodes (LEDs), have already been known for some time.
Electroluminescent materials are substances which are capable of emitting light on application of an electric field. The physical model for describing this effect is based on the recombination of electrons and electron holes, with emission of light. In light-emitting diodes, the charge carriers are injected into the electroluminescent material via the negative electrode or positive electrode. Electroluminescent devices contain a luminescent material as light-emitting layer. Electroluminescent materials and devices have been described in general terms, for example, in Ullmann""s Encyclopedia of Industrial Chemistry, Vol. A9, 5th Ed., VCH Verlag, 1987 and the references cited therein. Besides inorganic substances, such as ZnS/Mn or GaAs, organic compounds have also been disclosed as EL materials.
A description of EL devices containing low-molecular-weight organic EL materials is given, for example, in U.S. Pat. No. 4,539,507.
Although good results have been achieved using such materials, the property profile of such compounds leaves plenty of room for improvement.
Since, in addition, the development of electroluminescent materials can in no way be regarded as complete, the manufacturers of illumination and display devices continue to be interested in a very wide variety of electroluminescent materials for such devices.
One of the reasons for this is that only the interaction of the electroluminescent material with the other components of the devices allows conclusions to be drawn on the suitability of the electroluminescent material too.
The object of the present invention was therefore to provide novel electroluminescent materials which, on use in illumination or display devices, are suitable for improving the property profile of these devices.
Surprisingly, it has now been found that certain derivatives of triptycene are particularly suitable for use as electroluminescent materials.
The invention therefore relates to the use of a triptycene derivative of the formula (I) in electroluminescent devices, 
where the symbols in the formula have the following meanings:
K1, K2 and K3 are identical or different and are mono- or polycyclic systems, which may, if desired, contain heteroatoms, preferably N, S and/or O, and are substituted or unsubstituted;
X and Y are identical or different and are CR1, N, P, As or SiR2;
R1 are identical or different and are H, halogen, pseudohalogen or a hydrocarbon radical having 1 to 30 carbon atoms, which may also, if desired, contain heteroatoms, preferably xe2x80x94Oxe2x80x94, xe2x80x94Nxe2x80x94 and/or xe2x80x94Sxe2x80x94;
R2 are identical or different and are a hydrocarbon radical having 1 to 30 carbon atoms, which may also, if desired, contain heteroatoms, preferably xe2x80x94Oxe2x80x94, xe2x80x94Nxe2x80x94 and/or xe2x80x94Sxe2x80x94.
Compounds of the formula (I) are distinguished by adequate to good solubility in common organic solvents, good film-forming properties and a reduced tendency toward crystallization. The production of electroluminescent devices is thus simplified and their life extended. The emission properties of the compounds employed in accordance with the invention can be adjusted over the entire range of the visible spectrum through the choice of suitable substituents. In addition, the covalently bonded arrangement of the various parts of the triptycene compound allows a molecular structure such that certain properties can be set independently in different parts of the molecule. Thus, one part can have, for example, charge-transport or charge-injection properties, while the other has light-emitting properties.
At least one of the systems K1-3 is preferably a fluorophore. For the purposes of the invention, a fluorophore is an atomic group which imparts fluorescence on the triptycene derivative, for example an extended aromatic system.
It is furthermore preferred for all three systems K1-3 to be conjugated. Preferred, substituted or unsubstituted and/or bicyclic or polycyclic conjugated systems are: 
where Qxe2x95x90S, O or NR2.
Particularly preferred compounds of the general formula (I) are triptycene derivatives of the formula (II) and of the formula (III) 
where the symbols and indices have the following meanings:
X, Y, U and V are identical or different and are CR1, N, P, As or SiR2;
R1 are identical or different and are H, halogen, pseudohalogen or a hydrocarbon radical having 1 to 30 carbon atoms, which may also, if desired, contain heteroatoms, preferably xe2x80x94Oxe2x80x94, xe2x80x94Nxe2x80x94 and/or xe2x80x94Sxe2x80x94;
R2 are identical or different and are a hydrocarbon radical having 1 to 30 carbon atoms, which may also, if desired, contain heteroatoms, preferably xe2x80x94Oxe2x80x94, xe2x80x94Nxe2x80x94 and/or xe2x80x94Sxe2x80x94.
R3 are identical or different and are, F, Cl, Br, I, CN, NO2, a branched or unbranched alkyl group having 1 to 22 carbon atoms, where one or more xe2x80x94CH2xe2x80x94 groups may be replaced by xe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94, xe2x80x94SO3xe2x80x94, xe2x80x94Oxe2x80x94COxe2x80x94, xe2x80x94COxe2x80x94Oxe2x80x94, aryl or heteroaryl (in each case having 4 to 10 carbon atoms), with the proviso that two oxygen atoms cannot be bonded directly to one another, and where one, more or all H atoms may be replaced by F, and where two substituents R2 on the same ring may be linked to one another to form a ring or a further fused ring system or may also be hydrogenated, if desired partially, and may carry substituents, preferably of the type R1, with the proviso that the number of substituents is not greater than the total number of carbon atoms;
n are identical or different and are 0, 1, 2, 3, 4 or 5;
A and B are identical or different and are groups of the formula
(xe2x80x94M)a(xe2x80x94E)b(xe2x80x94M)cxe2x80x94(xe2x80x94E)d(xe2x80x94M)e(xe2x80x94E)f(xe2x80x94M)g(xe2x80x94E)hxe2x80x94R4
where the symbols and indices have the following meanings:
M are identical or different and are xe2x80x94CR5xe2x95x90CR6, xe2x80x94Cxe2x89xa1Cxe2x80x94, xe2x80x94CR7xe2x95x90Nxe2x80x94 or xe2x80x94Nxe2x95x90CR7xe2x80x94;
E are identical or different and are pyrazine-2,5-diyl, pyridazine-3,6-diyl, pyridine-2,5-diyl, pyrimidine-2,5-diyl, 1,3,4-thiadiazole-2,5-diyl, 1,3-thiazole-2,4-diyl, 1,3-thiazole-2,5-diyl, thiophene-2,4-diyl, thiophene-2,5-diyl, naphthalene-2,6-diyl, naphthalene-1,4-diyl or naphthalene-1,5-diyl, in which one or two CH groups may be replaced by N, 1,3-oxazole-2,4-diyl, 1,3-oxazole-2,5-diyl, 1,3,4-oxadiazole-2,5-diyl, 4,4xe2x80x2-bi-phenylene, anthracenediyl, carbazolediyl, benzoxazolediyl, indene-2,5-diyl or indene-2,6-diyl, where one or more H atoms in the ring systems may be substituted by radicals R8;
R4, R5, R6 and R7 are identical or different and are
a) hydrogen, xe2x80x94F, xe2x80x94Cl, xe2x80x94CF3, xe2x80x94CN or NR9R10,
b) a straight-chain or branched alkyl radical (with or without an asymmetrical carbon atom) having 1 to 20 carbon atoms, where
b1) one or more non-adjacent and non-terminal CH2 groups may be replaced by xe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94, xe2x80x94COxe2x80x94, xe2x80x94COxe2x80x94Oxe2x80x94, xe2x80x94Oxe2x80x94COxe2x80x94, xe2x80x94Oxe2x80x94COxe2x80x94Oxe2x80x94 or xe2x80x94Si(CH3)2xe2x80x94, and/or
b2) one or more CH2 groups may be replaced by xe2x80x94CHxe2x95x90CHxe2x80x94, xe2x80x94Cxe2x89xa1xe2x80x94Cxe2x80x94, cyclopropane-1,2-diyl, 1,4-phenylene, 1,4-cyclohexylene or 1,3-cyclopentylene, and/or
b3) one or more H atoms may be replaced by F, CN and/or Cl;
R8 are identical or different and are
a) xe2x80x94F, xe2x80x94Cl, xe2x80x94CF3, xe2x80x94CN or NO2 
b) a straight-chain or branched alkyl radical (with or without an asymmetrical carbon atom) having 1 to 20 carbon atoms, where
b1) one or more non-adjacent and non-terminal CH2 groups may be replaced by xe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94, xe2x80x94COxe2x80x94, xe2x80x94COxe2x80x94Oxe2x80x94, xe2x80x94Oxe2x80x94COxe2x80x94, xe2x80x94Oxe2x80x94COxe2x80x94Oxe2x80x94, xe2x80x94NHxe2x80x94, N(C1-C10-alkyl), xe2x80x94N-phenyl-, xe2x80x94N-tolyl-, xe2x80x94N(C2H5xe2x80x94OCH3)xe2x80x94 or xe2x80x94Si(CH3)2xe2x80x94, and/or
b2) one or more CH2 groups may be replaced by xe2x80x94CHxe2x95x90CHxe2x80x94, xe2x80x94Cxe2x89xa1Cxe2x80x94, 1,4-phenylene, and/or
b3) one or more H atoms may be replaced by F, CN and/or Cl;
R9 and R10 are identical or different and are
a) hydrogen,
b) a straight-chain or branched alkyl radical (with or without an asymmetrical carbon atom) having 1 to 20 carbon atoms, where
b1) one or more CH2 groups which are not adjacent to one another or to the nitrogen may be replaced by xe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94, xe2x80x94COxe2x80x94, xe2x80x94COxe2x80x94Oxe2x80x94, xe2x80x94Oxe2x80x94COxe2x80x94, xe2x80x94Oxe2x80x94COxe2x80x94Oxe2x80x94 or xe2x80x94Si(CH3)2xe2x80x94, and/or
b2) one or more CH2 groups may be replaced by xe2x80x94CHxe2x95x90CHxe2x80x94, xe2x80x94Cxe2x89xa1Cxe2x80x94, cyclopropane-1,2-diyl, 1,4-phenylene, 1,4-cyclohexylene or 1,3-cyclopentylene, and/or
b3) one or more H atoms may be replaced by F, CN and/or Cl and
b4) R8 and R9 together may also form a ring;
a, b, c, d, e, f, g and h, independently of one another, are 0 or 1. The sum of the indices is preferably at least 1, particularly preferably at least 2. The sum b+d+f+h is particularly preferably xe2x89xa71, very particularly preferably xe2x89xa72.
Particularly preferred compounds of the formula (I) are the compounds of the formulae (IV), (V) and (VI), 
where the groups A and B are as defined above.
Particularly preferred compounds of the formulae (IV), (V) and (VI) are those of the formulae (IV), (V) and (VI) a-i: 
where the radicals R1-11 are as defined for R3 in the formulae (II) and (III), and Y is O, S, NR11 or CR10R11.
The invention also relates to triptycene derivatives in which at least one of the groups K1-3 is a fluorophore. The invention likewise relates to triptycene derivatives of the formulae (II) and (III) in which the sum of the indices a-h is at least 1, preferably at least 2.
The triptycene compounds according to the invention are prepared by methods known per se from the literature, as described in the standard works of organic synthesis, for example Houben-Weyl, Methoden der Organischen Chemie [Methods of Organic Chemistry], Georg-Thieme-Verlag, Stuttgart, and in the corresponding volumes of the series xe2x80x9cThe Chemistry of Heterocyclic Compoundsxe2x80x9d by A. Weissberger and E. C. Taylor (editors).
The preparation is carried out under reaction conditions which are known and suitable for said reactions. Use can also be made here of variants which are known per se, but are not mentioned here in greater detail.
Compounds of the formula (II) can be synthesized, for example, starting from substituted triptycene or a heterotriptycene parent compound, which is in turn accessible by various synthetic routes. The following may be mentioned by way of example, but not in a restrictive manner:
1. Synthesis from substituted anthracene (or substituted acridine or substituted phenazine) and dehydroaromatic compounds, for example starting from
a) substituted o-fluorobromobenzenes with reactive metals, such as, for example, magnesium, for example analogously to G. Wittig, Org. Synth. IV 1963, 964;
b) substituted o-dihalobenzenes and butyllithium with elimination of metal halide, for example analogously to H. Hart, S. Shamouilian, Y. Takehira, J. Org. Chem. 46 (1981) 4427;
c) substituted monohalobenzenes and strong bases with elimination of hydrogen halide, for example analogously to P. G. Sammes, D. J. Dodsworth, J. C. S. Chem. Commun. 1979, 33;
d) substituted anthranilic acid derivatives and isoamyl nitrile, for example analogously to C. W. Jefford, R. McCreadie, P. Mxc3xcller, B. Siegfried, J. Chem. Educ. 48 (1971) 708;
e) a review of the preparation of a series of substituted dehydroaromatic compounds is given in Houben-Weyl, Methoden der Organischen Chemie [Methods of Organic Chemistry], 4th Edition 1981, Volume V/2b, pp. 615, Georg-Thieme-Verlag, Stuttgart.
2. Synthesis by deamination of substituted anthracene-9,10-imines, for example analogously to L. J. Kricka, J. M. Vernon, J. C. S. Perkin I, 1973, 766.
3. Synthesis by cycloaddition of substituted 1,4-quinones with substituted anthracene derivatives, for example analogously to E. Clar, Chem. Ber. 64 (1931) 1676; W. Theilacker, U. Berger-Brose, K. H. Beyer, Chem. Ber. 93 (1960) 1658; P. D. Bartlett, M. J. Ryan, J. Am. Chem. Soc. 64 (1942) 2649; P. Yates, P. Eaton, J. Am. Chem. Soc. 82 (1960) 4436. V. R. Skvarchenko, V. K. Shalaev, E. I. Klabunovskii, Russ. Chem. Rev. 43 (1974) 951.
Further syntheses of substituted triptycenes are given by way of example in C. F. Wilcox, F. D. Roberts, J. Org. Chem. 30 (1965) 1959; T. H. Regan, J. B. Miller, J. Org. Chem. 32 (1967) 2798.
Further syntheses of heterotriptycenes are given, for example, in D. Hellwinkel, W. Schenk, W. Blaicher, Chem. Ber. 111 (1978) 1798; or D. Hellwinkel, W. Schenk, Angew. Chem. 24 (1969) 1049; N.P. McCleland, J. B. Withworth, J. Am. Chem. Soc. (1927) 2753; N. A. A. Al-Jabar, A. G. Massey, J. Organomet. Chem. 287 (1985) 57.
Compounds of the formula (III) can be synthesized, for example, starting from a substituted bistriptycene parent compound or heterobistriptycene parent compound, which is in turn accessible via various synthetic routes. The following may be mentioned by way of example, but not in a restrictive manner:
1) synthesis from substituted anthracene (or substituted acridine or substituted phenazine) and substituted didehydrobenzenes, for example analogously to H. Hart, S. Shamouilian, Y. Takehira J. Org. Chem. 46 (1981) 4427;
2) synthesis by cycloaddition of substituted anthracene derivatives with 1,4-benzoquinone, for example analogously to E. Clar, Chem. Ber. 64 (1931) 1676; P. Yates, P. Eaton, J. Am. Chem. Soc. 82 (1960) 4436; W. Theilacker, U. Berger-Brose, K. H. Beyer, Chem. Ber. 93 (1960)1658.
Further syntheses are given by way of example in H. Hart, A. Bashir-Hashemi, J. Luo, M. A. Meador, Tetrahedron 42 (1986) 1641; V. R. Skvarchenko, V. K. Shalevb, E. I. Klabunovskii, Russ. Chem. Rev. 43 (1974) 951; V. R. Skvarchenko, A. G. Shil""nikova, N. N. Konrat""eva, R. Ya. Levina, J. Org. Chem. USSR (Engl.trans.) 3 (1967) 1477.
The further functionalization of the parent compounds described above can be carried out, for example, starting from the corresponding 1,4-dialkyl or 1,4-dimethyl derivatives, the corresponding groups for the synthesis of the groups A and B in the compounds of the general formulae (II) and (III) being formed by halogenation or oxidation to the aldehyde or carboxylic acid. The following syntheses may be mentioned by way of example: Zaug, Rapalla, Org. Synth. 27 (1947) 84; Trahanovsky, Young, J. Org. Chem. 31 (1996) 2033; San Filippo, J. Org. Chem. 42 (1977) 2182; {dot over (E)}tard, Ann., Chim. Phys. 22 (1881) 218; Sharpless J. Am. Chem. Soc. 97 (1975) 5927.
Introduction of groups for the synthesis of the groups A and B in the compounds of the general formulae (II) and (III) can likewise be achieved starting from the triptycene- or bistriptycenequinones. Thus, reaction of the quinones with organometallic reagents with subsequent didehydroxylation enables the introduction of various groups, such as, for example, alkyl, aryl or alkynyl. The following may be mentioned as examples of correspondingly analogous reactions: T. Imamoto, N. Takiyama, K. Nakamura, T. Hatajima, Y. Kamiya, J. Am. Chem. Soc., 111 (1989) 4392; A. Fischer, G. N. Henderson, Tetrahedron Lett. 24 (1983) 131; H. M. Crawford, J. Am. Chem. Soc. 70 (1948) 1081; C. T. Wigal, J. D. McKinley, J. Coyle, D. J. Porter, D. E. Lehman, J. Org. Chem. 60 (1995) 8421; or the corresponding chapters in Houben-Weyl, Methoden der Organischen Chemie [Methods of Organic Chemistry], Georg-Thieme-Verlag, Stuttgart. For the didehydroxylation, which can be carried out very effectively using low-valence titanium or tin or phenylhydrazine, reference can be made by way of example to the following: G. Solladie, A. Girardin, J. Org. Chem. 54 (1989) 2620 or M. lyoda, T. Yamauchi, M. Oda, J. C. S. Chem. Commun., 1986, 303; K. J. Clark, J. Chem. Soc. (1956) 1511.
Starting from the triptycene- or bistriptycenehydroquinones, after conversion into the corresponding triflates, mesylates or nonaflates, both palladium-catalyzed coupling or polymerization can be carried out, for example using organotin compounds analogously to Z. Bao, W. K. Chan, L. Yu, J. Am. Chem. Soc. 117 (1995) 12426; A. M. Echavarren, J. K. Stille, J. Am. Chem. Soc 109 (1987) 5478. K. Ritter, Synthesis (1993) 735. Furthermore, the triflates or mesylates, which are readily accessible from the hydroquinones, can also be coupled with organoboronic acids, for example analogously to T. Oh-e, N. Miyaura, A. Suzuki, Synlett (1990) 221; A. R. Martin, Y. Yang, Acta Chem. Scand. 47 (1993) 221; J. M. Fu, V. Sniekus, Tetrahedron Lett. 29 (1988) 1665; V. Percec, S. Okita, J. Polym. Sci. A 31 (1993) 877. In addition, the triflates and mesylates are starting materials for nickel-catalyzed C-C coupling, for example analogously to V. Percec, J. Y. Bae, M. Zhao, D. H. Hill, J. Org. Chem. 60 (995) 176; V. Percec, C. Pugh, E. Cramer, S. Okita, R. Weiss; Macromol. Symp. 54/55 (1992) 113. V. Percec, S. Okita, R. Weiss, Macromolecules 25 (1992) 1816; Y. Yamashita, Y. Inoue, T. Kondo, H. Hashimoto, Chem.Lett. (1986) 407;
For the synthesis of the groups A and B, reference may furthermore be made, for example, to J. S. Schumm, D. L. Pearson, J. M. Tour, Angew.Chem. 106 (1994) 1445; or to DE-A 23 44 732, 24 50 088, 24 29 093, 25 02 904, 26 36 684, 27 01 591 and 27 52 975 for compounds containing 1,4-phenylene groups, DE-A 26 41 724 for compounds containing pyrimidine-2,5-diyl groups; DE-A 40 26 223 and EP-A 0 391 203 for compounds containing pyridine-2,5-diyl groups; DE-A 32 31 462 for compounds containing pyridazine-3,6-diyl groups; N. Miyaura, T. Yanagi and A. Suzuki in Synthetic Communications 11 (1981) 513 to 519, DE-C-3 930 663, M. J. Sharp, W. Cheng, V. Snieckus in Tetrahedron Letters 28 (1987), 5093; G. W. Gray in J. Chem. Soc. Perkin Trans II, (1989) 2041 and Mol. Cryst. Liq. Cryst. 172 (1989) 165, Mol. Cryst. Liq. Cryst. 204 (1991) 43 and 91; EP-A 0 449 015; WO 89/12039; WO 89/03821; EP-A 0 354 434 for the direct linking of aromatics and heteroaromatics.
The preparation of disubstituted pyridines, disubstituted pyrazines, disubstituted pyrimidines and disubstituted pyridazines is described, for example, in the corresponding volumes of the series xe2x80x9cThe Chemistry of Heterocyclic Compoundsxe2x80x9d by A. Weissberger and E. C. Taylor (editors).
The compounds of the formula (I) according to the invention are suitable for use as electroluminescent materials.
For the purposes of the present invention, the term xe2x80x9celectroluminescent materialsxe2x80x9d is taken to mean materials which are used as or in an active layer in an electroluminescent device. The term xe2x80x9cactive layerxe2x80x9d means that the layer is capable of emitting light on application of an electric field (light-emitting layer) and/or that it improves the injection and/or transport of positive and/or negative charges (charge-injection or charge-transport layer). In addition, use as an electron-blocking layer or hole-blocking layer is also an application in accordance with the invention.
The invention therefore also relates to the use of a triptycene derivative of the formula (I) as electroluminescent material.
In order to be used as electroluminescent materials, the triptycene derivatives of the formula (I) are generally applied to a substrate in the form of a film by known methods familiar to the person skilled in the art, such as dipping, spin coating, vapor deposition or buffering under reduced pressure.
The invention thus likewise relates to an electroluminescent device having one or more active layers, where at least one of these active layers contains one or more triptycene derivatives of the formula (I). The active layer can be, for example, a light-emitting layer and/or a charge-transport layer and/or a charge-injection layer. The general construction of electroluminescent devices of this type is described, for example, in U.S. Pat. No. 4,539,507 and U.S. Pat. No. 5,151,629.
They usually contain an electroluminescent layer between a positive electrode and a negative electrode, where at least one of the electrodes is transparent to at least part of the visible spectrum. In addition, one or more electron-injection and/or electron-transport layers can be introduced between the electroluminescent layer and the negative electrode and/or one or more hole-injection and/or hole-transport layers can be introduced between the electroluminescent layer and the positive electrode. Suitable negative electrodes are preferably metals or metal alloys, for example Ca, Mg, Al, In or Mg/Ag. The positive electrodes can be metals, for example Au, or other metallically conducting substances, such as oxides, for example ITO (indium/tin oxide), on a transparent substrate, for example made of glass or a transparent polymer.
In operation, the negative electrode is set to a negative potential compared with the positive electrode. Electrons are injected by the negative electrode into the electron-injection layer/electron-transport layer or directly into the light-emitting layer. At the same time, holes are injected by the positive electrode into the hole-injection layer/hole-transport layer or directly into the light-emitting layer.
The injected charge carriers move through the active layers toward one another under the effect of the applied voltage. This results in electron/hole pairs recombining at the interface between the charge-transport layer and the light-emitting layer or within the light-emitting layer with emission of light. The color of the emitted light can be varied by means of the materials used as light-emitting layer.
Electroluminescent devices are used, for example, as self-illuminating display elements, such as control lamps, alphanumeric displays, signs and in opto-electronic couplers.
Compounds of the formula (I) are furthermore suitable, for example, for use in optical storage media, as photorefractive materials, for nonlinear optical (NLO) applications, as optical brighteners and radiation converters and, preferably, as hole-transport materials in photovoltaic cells, as described, for example, in WO-A 97/10 617 and DE-A 197 11 713, which are expressly incorporated herein by way of reference.
The invention is explained in greater detail by the examples, without this being intended to represent a limitation.